Refrigerating apparatus



Sept. 23', 1941 A. O. GROOMS REFR IGERAT ING APPARATUS Filed Jan. 31, 1939 2 Sheets-Sheet l P 1941- A. o. GROOMS 2,256,671

REFRIGERAT ING APPARATUS Filed Jan.'3l, 1939 2 Sheets-Sheet 2 INVENT OR.

ATTORNEYS Mama's a bHtAKt-Rs,

Patented Sept. 23, 1941 REFRIGERATING APPARATUS Albert 0. Grooms, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application January 31, 1939, Serial No. 253,833

13 Claims.

This invention relates generally to controls sealed against dirt and moisture.

Sealed controls such as sealed switches and valves are desirable to prevent tampering and to exclude dirt, moisture and corrosion. When pressure-operated means are used to operate such control, the change in temperature of the air within the sealed casing will change the operating pressure of the control. In some appli cations this change is not great enough to be objectionable but in other applications, especially where the casing is subjected to great changes in temperature it is desirable to prevent this change which affects the setting of the control. In other installations it is desirable to provide a greater change in the setting of the control according to the change in temperature, sometimes in the same direction and sometimes in the opposite direction to the above natural change.

It is an object of my invention to provide a sealed pressure-operated control in which the change in temperature and pressure of the sealed casing will not change the setting of the control.

It is another object of my invention to provide a sealed pressure-operated control in which the change in temperature and pressure of the sealed casing will change the setting of the control in the direction and at the rate desired.

It is another object of my invention to provide a sealed pressure-operated switch in which the rise in temperature of the sealed casing and the rise in pressure of the pressure operated means will cause the switch to close and will increase the length of the closed periods of the switch and decrease the open periods of the switch.

It is another object of my invention to provide an improved environmental condition for the switch contacts in a sealed switch.

It is still another object of my invention to provide a simple sealed control for room coolers and air tempering devices having outside temperature compensation.

It is still another object of my invention to provide a simple sealed control for refrigerators which is provided with means for compensating for varying temperatures outside the compartment to be cooled.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a view partly diagrammatic of a household refrigerator embodying one form of my invention;

Fig. 2 is a sectional view of a control means for the refrigerator shown in Fig. l; and

Fig. 3 is a view partly diagrammatic of a refrigerating system for cooling a room, together with another form of my improved control means.

Briefly, in the first form shown I have provided an ordinary household refrigerator with a thermostat control having a sealed casing for the switch mechanism. The switch mechanism is operated by a bellows connected to a thermostat bulb on the evaporator in the usual manner, and the casing is provided with an additional bellows which is operably connected to the switch mechanism so as to provide a change in the operating characteristics of the switch mechanism which is in the opposite direction to the change in operating characteristics caused by changing pressures within the sealed casing. When the second bellows is so proportioned that the effect of the pressure thereon causes an effect upon the switch mechanism which is exactly equal to and opposite to the effect of the pressure within the sealed casing upon the primary bellows, the switch will be fully compensated for the change in pressure within the casing.

In the second form of my device the primary bellows is connected to a thermostat bulb located outside of the room to be cooled. The second bellows is merely used as a seal for the external adjustment and the casing is provided with a volatile fluid or an absorbent and a gas which changes the pressure within the sealed casing in accordance with the temperature of the sealed casing. The switch normally operates according to the temperature and pressure within the sealed casing and is compensated for changes in outdoor temperature by the primary bellows.

Referring now to the drawings and more particularly to Fig. 1 there is shown a refrigerator cabinet generally designated by the reference character 20, containing a food compartment 22 kept cool by a refrigerant evaporating means 24 located within the food compartment. The refrigerant evaporating means 24 is supplied with liquid refrigerant by the refrigerant liquefying means which includes a compressor 26 driven by an electric motor 28 for withdrawing evaporated refrigerant from the evaporating means 24 through the return conduit 30. The refrigerant so withdrawn is compressed by the compressor 26 and forwarded to the condenser 32 where the compressed refrigerant is liquefied and collected in the receiver 34. From the receiver 34 the liquid ,pfrigerant is forwarded through a supply conduit 36 under the control of a suitable restrictor 38 to the evaporating means 24.

The operation of the electric motor 28 is controlled by a sealed switch 40 which is connected by capillary tubing 42 to a thermostat bulb 44 mounted upon and in heat exchange relation with the evaporating means 24. The sealed control switch 40 is mounted in a suitable location outside the insulated food compartment so that it is responsive to the temperature of the air in the room. It is provided with terminals 46 and 48 which are connected to the conductors 50 and 52 which connect to the electric motor 28 and to the source of power.

The switch 40 is provided with a sealed casing 54 which contains the primary bellows 56 which is connected to the end of the capillary tubing 42. The primary bellows 56 acts upon the primary lever 58 which is pivoted upon the pivot pin 60. At the opposite end, the primary lever 58 is pivotally connected to a double toggle snap acting mechanism including secondary lever 62 which in turn is connected by a tension toggle spring 64 to a contact carrying lever 66 provided with a contact 68 and a stop 70 which cooperates with the fixed stop 12 formed of insulating material.

The contact 68 cooperates with the stationary contact 14 which is mounted upon an insulating bushing 16 which is sealed to the casing 54. The contact 74 forms the head of a screw which extends through the insulating bushing 16 to the outside of the casing 54 and forms the terminal 46 to which the conductor 50 is fastened. The pivot 18 for the contact lever 66 is likewise formed on the inner end of the terminal screw 48 which is connected to the conductor 52 and which is sealed within the insulating bushing 80 provided in the wall of the sealed casing 54. The terminals 46 and 48 may be molded into their respective bushings so as to provide a perfect seal and these bushings may be sealed to the adjacent wall portions of the casing by a suitable sealing compound 82, such as solidified asphalt.

Heretofore when such a sealed switch was located outside the insulated food compartment of a household refrigerator of this type, an increase in room temperature, for example from 70 F. to 110 F. would increase the temperature of the air within the sealed casing and cause a corresponding increase in pressure within the casing of about 2 lbs. per square inch, and this increase in pressure would oppose the expansion of the primary bellows 56 and thereby would oppose the tendency of the switch to close and would thus raise about 4 F. or F. the temperature of the evaporating means at which the switch would open and close. An increase in room temperature, however, causes an increase in heat leak into the food compartment thereby raising the food cornpartment temperature even when the evaporating temperature is kept the same. Obviously upon an increase in the temperature of the room and of the food compartment 22 it is desirable to lower the temperature of the evaporating means 24 so as to obtain increased refrigeration. Thus this change in switch operation was in the opposite direction to the desired change. A much lesser change in switch operation occurs when the sealed casing is located in the food compartment where the temperature fluctuations are much less.

In order to prevent this undesired change in the operation of the switch mechanism, according to my invention I provide a second bellows 86 having its open end sealed to the wall of the sealed casing 54 and its closed end extending into the casing. This second bellows 86 is located upon the opposite side of the primary lever 58 from the primary bellows 56. This second bellows 86 is connected to the primary lever 58 by a compression type coil spring 88. Thus the bellows 56 and 86 tend to act upon the primary lever 58 in opposite directions. With this construction, when the pressure within the sealed casing 54 increases, the expansion of the bellows 56 will be opposed to a greater extent but expansion of the second bellows 86 will also be opposed. The effective area of the two bellows as well as their effective moment arms with respect to the primary lever and the characteristics of the compression springs will determine their relative effect. If the two bellows are of the same size and characteristics the effect of pressure upon the two bellows will be equal, but the effect upon the primary lever will be in accordance with their moment arms and the characteristics of the compression springs. Thus if an increased pressure within the sealed casing 54 reduces the net force of the primary bellows 56 the increase in pressure will also tend to collapse the second bellows 86 to reduce the tension of the compression spring 88 which opposes the expansion of the bellows 56. Thus by the increase in pressure upon the second bellows the tension of the compression spring is reduced and this may be proportioned so as to exactly compensate for the effect of the pressures upon the primary bellows 56 in order that the setting of the switch will not be changed, or to over compensate for such pressures in order to lower evaporator temperatures when the room temperature and compartment temperature rises. When the casing is located inside the food compartment it may change the evaporator temperatures according to changes in food compartment temperature.

The second bellows 86 also serves as a means for sealing the external adjustment for the switch. In order to provide this external adjustment, a compression spring 90 is provided within the second bellows 86 and extends between the closed end of the second bellows 86 and a spring retainer 92 which is provided upon the lower end of the adjusting screw 94 threaded into the block 98 in the adjacent wall portion of the sealed casing and provided with a finger manipulator 86 at its outer end. Thus by turning the adjusting screw 84, the tension of the spring 90 within the second bellows 86 will be changed thereby changing the setting of the switch accordingly. By in creasing the size of the second bellows 86 with respect to the primary bellows 56 the switch will be over compensated for the change in pressure and temperature of the sealed casing and this will increase the tendency of the switch to close under such conditions and thereby will compensate for the increase in temperature of the food compartment. Therefore by making a second bellows larger in proportion to the primary bellows 56 the switch may be made to compensate for the changes in temperature of the room and of the food compartment 22. Instead of changing the relative sizes of the bellows, the spring characteristics or the effective moment arm may be changed. This is desirable in order to maintain more constant temperatures within food compartment 22.

Instead of air, other fluids may be used within the sealed casing 54 and preferably some inert gas, such as nitrogen or argon may be used or some volatile liquid may be used within the sealed casing ePreferably all oxygen is removed from the interior of the sealed casing so as to prevent burning of the contacts 68 and T4. If desired some suitable absorbent such as activated charcoal, or activated silica I06 may be provided in the bottom of the sealed casing 54 and held in place by a screen I08. Such substances absorb and evolve gases according to changes in temperature and will provide greater changes in pressure than is possible under the gas laws. This is especially desirable when it is desired to use the over compensated form within the food compartment. The absorbent substances may be used with inert gases such as nitrogen, argon and carbon dioxide. Other absorbents such as calcium chloride may also be used. The thermostat bulb 44 may also be filled with either activated charcoal or Silica Gel and may be charged with some suitable absorbent such as carbon dioxide, nitrogen or dimethylether.

By changing the amount of charcoal in the thermostat bulb 44 and in the sealed casing 54 and by changing the charging pressures and temperatures of the various gases used in the thermostat bulb 44 and the sealed casing 54, a wide latitude in the design conditions of the switch mechanism, together with the bellows and springs is thus made possible. However, instead of charcoal and gases, any suitable volatile liquid may be used in the thermostat bulb 44 and the sealed casing 54.

In Fig. 3 a different form of the invention is shown as applied to a room cooler. In this figure the room, generally designated by the reference character 210, is illustrated by a dot and dash line. Within this room 2H] is a room cooler 2| 2 provided with an air inlet 2'! 4 and an air outlet 2|6 and an electric fan 2|8 for drawing air from the room through the inlet H4 and forcing air through the outlet 2|6. In the path of the air flowing from the inlet to the outlet is a refrigerant evaporating means 220 which is supplied with liquid refrigerant from a liquefying means which includes a compressor 222 driven by an electric motor 224 for compressing evaporated refrigerant withdrawn through the return conduit 226 from the evaporating means 220. frigerant is liquefied in the condenser 228 and collected in the receiver 230. From the receiver liquid refrigerant is forwarded through a supply conduit 232 under the control of a thermostatic expansion valve 234 to the evaporating means 220 where the refrigerant evaporates under reduced pressure and cools the air circulated through the room cooler.

In order to control the operation of this room cooling refrigerating system, I have provided another form of sealed thermostatic switch generally designated by the reference character 236. This sealed thermostatic switch controls the supply of current through the electric circuit 238 which supplies current to the compressor motor 224. The thermostat switch 236 is provided with a sealed casing 240 containing a closed bellows 242 connected by capillary tubing 244 to a thermostat bulb 246 preferably located in the air outside of the building in which the room 2l0 is located. This bellows 242 acts upon a primary lever 248 pivoted upon the pin 250 and connected at its opposite end t a secondary lever 252. The secondary lever 252 in turn is connected by a tog- This compressed regle spring 254 to the contact lever 256 which is pivoted on the pin 258.

The contact lever 256 is provided with a contact 258 which is adapted to engage the cooperating contact 266 provided as a head upon the terminal screw 262' which extends through the insulating bushing 264 provided in the wall 240. The terminal screw 262 is preferably hermetically sealed in the bushing 264 and the bushing is sealed to the wall 240. The terminal screw 264 is connected to the electric circuit 238. The pivot pin 258 is provided upon the end of the terminal screw 264 hermetically sealed in the insulating bushing 266 also sealed to the wall 240. A stop 268 of insulating material is provided for limiting the opening movement of the contact lever 258.

The expansion of the bellows 242' is opposed by a compression type coil spring 210 which extends between the primary lever 248 and the closed end of a sealing bellows 2'12 which is provided with an external screw threaded adjustment 214 for changing the tension of the spring 210. It should be noted that the pressure within the casing 240 will not collapse the bellows 212 since the screw 274 will prevent the movement of this bellows.

In room cooling it has been found desirable to change the temperature within the room according to the changes in outside temperature. For example, it is desirable to arrange the indoor temperatures in accordance with outdoor temperatures according to the following table:

Thus, as the outdoor temperature rises the differential between the outdoor and the indoor temperature rises. In order to provide a simple control which will control the system in such a manner I provide some means within the sealed casing 240 which will increase in pressure at a lesser rate than the means with which the outdoor bulb 246 is charged. The contacts are so arranged that increasing outdoor temperature will tend to open the contacts while increasing indoor temperature will tend to close the contacts. Thus when the outdoor temperature rises, a higher room temperature is necessary before the contacts will be moved to closed position.

Preferably the outdoor bulb 246 is charged with activated charcoal or activated silica in greater amount than the activated charcoal or activated silica which may be provided within sealed casing 240. Preferably nitrogen or argon is used as a gas in the sealed casing 240 and carbon dioxide or nitrogen or some other gas is used in the bellows 242 and the bulb 246. However, volatile liquids may be used instead and sulphur dioxide or carbon tetrachloride may be used in the casing 240, and isobutane or ethyl alcohol may be used in the thermostat bulb 246. Sufficient volatile liquid should be provided to fill the bellows 242 and an appreciable portion of the bulb 246. If desired, volatile liquids may be used in the sealed casing 240 and the adsorbents and gases may be used in the thermostat bulb 246 or vice versa. The activated charcoal or activated silica 2'" may be held in contact with the bottom wall of the sealed casing 240 by an enclosing screen 219. By being so located the activated charcoal or activated silica can readily adsorb and evolve some of the gas within the sealed casing according to the temperature of the walls of the casing zauwrn this way the switch mechanism may be made readily responsive to the temperature of the air within the room 2H]. If a volatile liquid is used in the sealed casing 240 it will likewise collect upon the walls thereof and be readily responsive to the temperature of the air in the room. Preferably the casing 240 should be located in the inlet air stream of the room cooler 2l2.

By this control the contacts are sealed and the room temperature is kept at a desirable figure according to changes in the outdoor temperature.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adapted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A control means including a fluid-tight sealed casing, a pressure-operated diaphragm means exposed on one side to the pressure within the free area of the interior of the sealed casing, a switch means operated to closed position upon an increase in pressure upon the other side of the diaphragm means, and means operated by the pressure within the free area of the interior of the sealed casing for reducing the diaphragm pressure necessary for moving the switch means to closed position.

2. A controlling means including a fluid-tight sealed casing, a pressure-operated diaphragm means exposed on one side to the interior of the sealed casing, a switch means operated to closed position upon an increase in pressure upon the other side of the diaphragm means, spring means for controlling the operation of the diaphragm means, and diaphragm means responsive to the pressure within the free area of the casing for changing the tension of said spring means.

3. A control means including a fluid-tight sealed casing, a pressure-operated diaphragm means exposed on one side to the interior or the sealed casing, a switch means operated to closed position upon an increase in pressure upon the other side of the diaphragm means, and a volatile fluid within the free area of said sealed casing for creating desired pressures therein to change the efiectiveness of said pressure-operated diaphragm means.

4. A control means including a fluid tight sealed casing, a pressure-operated diaphragm means exposed on one side to the pressure within the free area of the interior of the sealed casing, a switch means operated to closed position upon an increase in pressure upon the other side of the diaphragm means, and a second diaphragm means acting oppositely to said pressure-operated diaphragm means under the influence of the pressure within the free area of said sealed casing for changing the relation between the pressure acting upon said pressure-operated diaphragm and the operation of said switch means.

5. A control means including a fluid-tight sealed casing, a pressure-operated diaphragm means exposed to the interior of the sealed casin a means within the sealed casing operated by the diaphragm means, and means within said sealed casing for compensating for the efiect of the change in pressure within the free area or the sealed casing upon the diaphragm means.

6. A control means including a fluid-tight sealed casing, a pressure-operated diaphragm means exposed to the interior of the sealed casing, a means within the sealed casing operated by the diaphragm means, and compensating diaphragm means operating upon said first mentioned diaphragm means for compensating for the effect of pressure conditions within the free area of the sealed casing upon said first diaphragm means.

7. A control means including a fluid-tight sealed casing, a pressure-operated diaphragm means exposed to the interior of. the sealed casing, a means within the sealed casing operated by the diaphragm means, and a volatile fluid within said sealed casing for creating fluid pressures within the free area of the sealed casing for acting upon said diaphragm means.

8. A control means including a fluid-tight sealed casing, a pressure-operated diaphragm means exposed to the interior of the sealed casing, a means within the sealed casing operated by the diaphragm means, spring means for controlling the movement of the diaphragm means, and means operated by pressures within said free area of the sealed casing for changing the tension of said spring means.

9. A control means including a fluid-tight sealed casing, a pressure-operated diaphragm means exposed on one side to the interior of said sealed casing, a thermostat bulb, said thermostat bulb being charged with means for creating a pressure in accordance with its temperature, means for connecting said thermostat bulb and said diaphragm means for applying said pressure to the other side of said diaphragm means, said casing being charged with means for creating a change in pressure within the free area of said casing in accordance with a change in temperature of said casing which is greater than that provided by the gas laws.

10. A control means including a fluid-tight sealed casing, a pressure-operated diaphragm means exposed on one side to the interior of said sealed casing, a thermostat bulb, said thermostat bulb being charged with means for creating a pressure in accordance with its temperature, means for connecting said thermostat bulb and said diaphragm means for applying said pressure to the other side of said diaphragm means, said casing being charged with means for creating a change in pressure within the free area of said casing in accordance with a change in temperature of said casing, said last means having a lesser rate of change in pressure than the means in said thermostat bulb.

11. A control means including a fluid-tight sealed casing, a pressure-operated diaphragm means exposed on one side to the interior of said sealed casing, a thermostat bulb, said thermostat bulb being charged with means for creating a pressure in accordance with its temperature, means for connecting said thermostat bulb and said diaphragm means for applying said pressure to the other side of said diaphragm means, said casing being charged with an absorbent and an inert gas absorbed and evolved from the absorbent upon changes in temperature.

12. A control means including a fluid-tight sealed casing, a pressure operated diaphragm means exposed on one side to the pressure within the freearea in the interior of the sealed easing, a control device operated to a first position upon an increase in pressure upon the opposite side of the diaphragm means and to a second position upon a decrease in pressure upon said opposite side of the diaphragm means, and means an increase in pressure upon the opposite side of the diaphragm means and to a second position upon a decrease in pressure upon said opposite side of the diaphragm means, and means for creating desired pressures Within the free area of said sealed casing for changing the effectiveness of said diaphragm means to operate the control device.

ALBERT O. GROOMS. 

